Goodwill (Schedule of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Goodwill, Impairment Loss	$ 230,632	$ 0	$ 115,791	$ 0	$ (330,680)
Goodwill [Roll Forward]
Goodwill, Beginning Balance				596,103	596,103	114,963	113,701
Payments for (Proceeds from) Previous Acquisition						829	1,262
Goodwill, Ending Balance	265,423				265,423	596,103	114,963
Black Thunder [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss					115,800
Goodwill [Roll Forward]
Goodwill, Ending Balance				115,800
Parent [Member]
Goodwill [Roll Forward]
Payments for (Proceeds from) Previous Acquisition						829	1,262
ICG [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period						$ 480,311